Method of treating metals



Jan. 1, 1935- J. H. DE BATS 7 METHOD OF TREATING METALS Filed NOV. 20, 1951 ATTORN EYJ' Patented Jan. 1, 1935 BEST AWEHLDIN COPY UNITED; STATES PATENT OFFICE.

1,988,426 unnon or mama METALS 1 mum Louis in am, am Orange, N. .1. Application November :0, 1931, saw No. 576,367 9 Claims. (oi. 148-12) This invention relates to improvements in methods for uniformly hardening formed metal articles and to the product thereof.

Hitherto it has been proposed to harden metal articles by hammering after carbonizing and forming to desired-configuration. However, such methods have resulted in the compacting or densifying of the surface metal and layers without affecting or refining the grains of metal found 10 in the interior of the body of the article under treatment. Various methods have been proposed to effect a desired surface hardening, which methods generally include the impacting of me' tallic articles such as steel balls or hammer heads against the'surface'of the article to be treated, As pointed out above, such treatment, while altering the crystalline structure of and densifying the metal at or near the surface of the article under treatment, does not improve or refine the interior crystalline structure of said article due to the masking or inhibiting effect of the densifled metal deflecting blows over a path lying in the plane substantially perpendicular to the angle of impact. Where impacts are continued on a densifled surface of the type described, the surface is checked and cracked so that the beneflcial effects of the mechanical working are lost and other deleterious conditions set up which favor surface corrosion and serve as fool for fissures which are self-propagating and result in fractures. It is an object of this invention to provide. an

. improved process for hardening metals throughout by mechanical impact. It is a further object of thiseflvention to provide such an improved process in which the body of metal in an article to be hardened is subjected to diametrically opposed impacts. Yet another object of this invention is the provision of a process in which 40 an article to be uniformly hardened is subjected to a series of diametrically opposed impacts forminga substantially uniform plane of action. It is also a further object of this invention to provide an improved roll or other article of metal in whichthe grains of the metal have been uniformly refined by mechanical working.

Broadly stated, the invention contemplates treating metals or alloys in their solid state by subjecting the metal to a multiplicity of blows or impacts, preferably in rapid succession and with the aid of a metallic instrumentality. These blows are capable of causing a change in the'internal structure of the metal under treatment and a changein the physical properties thereof including decrease "in size of crystals, an increased is mounted a framework 5 which supports an air density, toughness and wearing characteristics, while at the same time preserving the external dimensions of the solid body of metal under treatmen Although the invention is applicable to many 5' difl'erent types of metal and alloy articles or pieces, it is particularly described herein as applied to the treatment of rolls made from a low carbon steel, which' have been hardened. The treatment according to this invention causes among other advantageous characteristics a rearrangement of the crystalline structure of the roll and makes the molecular structure more uniform, thereby increasing the density and toughness of the roll without altering its outside dimensions.

In accordance with one embodiment of the present invention, afterv a roll has been carbonized according to any of the well known processes, it is treated by the application of a multi- 20 plicity of blows or impacts in rapid succession, which changes the internal structure of the metal without altering its outside dimensions to any appreciable extent. The effects induced in the metal are preferably produced by the application of impacts, blows or shocks in rapid succession and in increasing intensity to the surface of the roll. T

In the drawing like numerals refer to similar parts throughout the several views,,of which Fig. 1 is a vertical elevation, partly in section, of an' apparatus suitable for carrying out the process;

hammer 6. A spring 7 is secured at its righthand end 8 to the framework 5 and supports on its upper surface a resilient cushion 9 of rubber" which is secured to the spring by a collar 10. The cushion 9 isplaced so that it is directly under the head 12 of the hammer. Secured to the lower surface of the left-hand end of the spring 7 is a second hammer head 13 made out of hardened steel.- Mounted on the carriage 4 diametrically oppos'ite thehammer head 13 isan anvil 14 also made out of hardened steel.

After the roll has been mounted in the lathe, the lathe is set in motion at a low speed of rotation and feed. Air is supplied to the hammer 6 through the air line 60, thereby causing the hammer head 12 to deliver rapid blows to-the flexible cushion 9. These blows are transmitted through the spring 7 to the hammer head 13, so that the hammer head 13 moves rapidly up and down impacting against the top of the roll. Each stroke of the hammer head 12 causes thehammer head 13 to vibrate up and down many times, thus allowing the hammer head to engage upon the surface of the roll, thereby inducing an action within the plane represented by a line between the hammer head and the anvil con;

tact point. The anvil 14 is secured to the carriage 4, so that it is in the same plane as the hammer head 13, and when the roll is being rotated, the anvil 14 contacts therewith so as .to limit the amplitude of the impact wave activity.

The feed of the carriage 4causes both the hammer head 13 and the anvil 14 to traverse the length of the roll, and, since the roll is being rotated, the entire surface thereof is subjected to a series of rapid blows or shocks. However, these shocks are not of sufficient intensity to cause substantial deformation or change in the outside dimensions of the roll, but on t it con-' .trary are only of suiiicient intensity to seat up a series of impact waves within the roll, "i which activity breaks down the crystalline structure and rearranges the thus formed smaller crystals, thereby densifying the structure "of' the metal. The impacts of the hammer head 13 should not be confused with the blows sometimes delivered, for example, by means of an air hammer tametal when it is desired to deform the metal. In that case, any change in the crystalline structure is due to a crushing or kneading of the crystals caused by the forcible impacting of the hammer, whereas, in the present process, the rearrangement of internal structure is believed to be due to the application of .a series of rapid impacts of relatively small force or intensity caused by the relatively light striking of the hammer head 13 on the surface of the roll. The relatively light impacts delivered by the hammer head 13 are effective for causing the rearrangement of internal structure without, however, altering the outside dimensions of the roll. The placing of the hammer head 13 and the anvil 14 in the same plane transversely of the axis of the roll and preferably diametrically opposite each other apparently has the effect of causing rearrangement of its internal structure. It is preferable to first subject the roll to relatively light impacts from the hammer head 13 and to increase theintensity of these impacts as the treatment progresses. Otherwise, there may be danger of cracking the roll. This increase of the. intensity of the impacts in the course of the treatment of the roll, is essentially a cyclical treatment .involving the impacting of the roll surface under blows of a given magnitude and the repetition of this treatment using blows of increasing. magnitudes.

The use of the method herein described on the roll, as an example, produces a product having practically all of its crystals broken up and moved into closer contact with each other and also gives a. product in which is found a. series of substantially uniformly sized crystals when passing from the exterior of the piece or roll towards the interior or center thereof, substanthe article along its length.

tiallyallofthemmuchsmallerthanthecrystals originally found in the 'roll or piece.

. The example herein set forth in this speciflcationis aroll which performs a function in contacting with other metals or articles, usually for h P 1 5 cles. I

When the product or piece has been subjected to the'method or process herein set-forth, it may be advisable, in some instances, to relieve any possible strain or stress existing within the piece. This stress or-strain relieving step may be accomplished in any suitable manner, such as for instance, by subjecting the article or piece to a comparatively low temperature 'for a relatively long time for accomplishing a good seasoning result.

While this description of a step in relieving the strain accomplishes'the desired result, it is to be understood that the temperature may vary considerably and that the time of being subjected to the temperature may vary considerably. The type of alloy or metal structure will control thesr features for the purpose of accomplishing these factors.

of forming or reshaping those arti- Referring more specifically to Figs. 2 and 3,

the novelresults secured by the application of the concepts of the present invention are believed to be due to the fact that by mechanically treating the surface of a roll or. article by suitable means, such as hammer blows, thelsaid roll or article being so supported that the anvil or support lies at a point on the article diametrically opposed to the hammer, the vibrations or waves set up in the metal are propagated in substantially the same plane and travel directly from opposed surfaces of the article-toward the center thereof, at which point they neutralize each other. In this substantially linear convergence of compression waves of equal and opposed strength and direction, the crystals of the metal in the body of the roll or article are uniformly worked and there is no localization of the effectat or near the surface resulting-in defor mation or super-hardening of such surface. By rotating the roll, as shown, at a slow rate of speed, these'beneficial effects are still further heightened by the application of the modifying or refining forces in a series of overlapping planes extending the length of. the roll and at right angles to the long axis, thereof, thus permitting uniform refining of the entire body of metal in the article,

As shown more particularly in Fig. 3, an impacting force 20 is opposed by an equal force 21, which forces converge at the center of the article and neutralize each other. If a point of support 22 is offset with respect to a point of impact 23, a series of waves 24 will be set up in the outer laye of the article to point 23 as a center and will ot travel through to the center of thearticle but ill travel along the surface of the article. Such an action can best be illustrated by the common experience of blacksmiths and metal workers in which; when hammering a metal sheet, or rod or other article, it is found that if the hammer blow falls on the article in the plane of the support for the article, no vibration is set up in the article being hammered. However, if the blow strikes the article ata point which is opposed with respect to the point of support for the article, vibrations are set up in It is at present believed that the lmiform hardness in the body of the roll or other article treated results from reformation of the crystalline structure due to the breakage or cleavage along the weakest slip planes so that substantially the greater part of the resulting crystals have their slip planes lying in directions transverse to the direction of application of the impacting or refining forces.

It will be noted from the foregoing description that there has been set forth and-described an improved method of producing a novel and improved metal or alloy product. It will further be noted that this method of operation on a piece or article produces in that piece or article, preferably by mechanical means, a change in the.

structure of the crystals, thereby forming a change in the structural nature of the piece, and usually this change results in the formation of a large number of smaller sized crystals compactly positioned in respect to each other and with relatively small size grain boundaries therebetween. In addition, the physical characteristics of this changed article or piece have been materially modified by the treatment resulting from the application of the ,method, and particular attention is called to the fact that the improved product has many satisfactory desired characteristics over the formation and structure of. the article before it was subjected to this treatment.

Athough the invention has been described in connection with the treatment of a carbonized roll, it is applicable to other articles having different chemical composition. The impacts of the hammer head 13 on the article may be caused manually, or a dlflerent type of hammer, such as an electric hammer, may be used in place of the air hammer 6.

I have described the present preferred method of carrying out my invention. It is to be understood, however, that the invention may be otherwise practiced within the scope of the following claims.

This case is in part a continuation of my application, Serial Number 499,261, filed December 1. 1930.

What is claimedis:

1. The method of treating hardened metal articles without deformation to refine the grain thereof and secure uniform hardness therein comprising supporting said articles and cyclically impacting same under increasing pressures and at points diametrically opposed to said point of support.

2. The method of treating hardened metal articles without deformation to refine the grain thereof and secure uniform hardness therein comprising supporting said articles and cyclically and progressively impacting same at diametrically opposed points, while rotating said article in a plane defined-by said points of impact.

3. The method of treating hardened metal ar ticles without deformation to refine the grain thereof and secure uniform hardness therein comprising supporting said articles and cyclically impacting same under increasing pressures and at diametrically opposed points, while rotating said article in a plane defined by said pointsof impact and progressively moving the article under treatment over said points.

4. The method of treating metal articles which comprises rotating a metal base and cyclically applying shocks of increasing magnitude to the surface thereof at diametrically opposed points whereby to cause an internal rearrangement therein without altering the outside dimensions of the metal.

5. The method of treating metal articles which comprises rotating a metal base and applying shocks to the surface thereof at diametrically opposed points whereby to cause an internal rearrangement therein without altering the outside dimensions of the metal, and thereafter repeating the process while applying shocks of increased magnitude.

6. The method of treating hardened metal articles which process comprises rotating a supported metal base and successively applying a .series of shocks of increasing magnitude to. the

entire surface thereof atdiametrically opposed points on the said surface, the said shocks being characterized by magnitudes insufficient to cause deformation of the surface of the articleworked upon. p

7. The method of treating hardened metal articles which comprises rotating a metal base and successively applying a series of diametrically opcomprising diametrically opposed impacts applied to the surface of said article.

JEAN HUBERT LOUIS DE BATS. 

